Electrodynamic pillow-type loudspeaker



I J. DJZIMMERMAN 2, 3,80 ELEGTRODYNAIIIC PILLOW-TYPE LOUDSPEAKER Filed Aug. 6. 1949 INVENTOR. JOSEPH D. ZIMMERMAN ATTORNEY Patented Sept. 26, 1950 ELECTRODYNAMIC PILLOW-TYPE LOUD- SPEAKER Joseph D. Zimmeruian, St. Paul, Minn.

Application August 6, 1949, Serial No. 108,945

My invention relates to a radio speaker of the dynamic type particularly adaptable as a pillow speaker.

It is a primary object of my invention to provide a moving coil dynamic speaker of a construction whereby the unit is relatively flat and which may be placed beneath a pillow and due to its thin nature is virtually imperceptible beneath the pillow. 7

It is a further primary object to provide a dynamic speaker having the pot assembly virtually within the concave portion of the cone of the speaker. Heretofore, dynamic speakers, although constructed very small in size, were thick relatively speaking, due to the fact that the pot assembly protruded outwardly of the apex or convex portion of the cone of the speaker. This construction produced a speaker which was not at all adaptable to be placed beneath a pillow due to its thickness, nor was this type of speaker adapted to be placed Where space was at a premium.

It is a further object of my invention to secure the voice coil form to the cone with the coil projecting from within the concave surface of the cone towards the pot assembly above mentioned, the voice coil form moving adjacent a permanent magnet secured centrally of the pot assembly. It is an additional object to provide a rear casing support for securing the pot assembly thereto and a perforated front casing portion. Thus, I have provided a new type of voice coil form, cone and pot construction producing a relatively flat speaker particularly adaptable as a pillow speaker of the dynamic type. have been of the magnetic type, which type of speaker gives poor reproduction as compared to a dynamic type of speaker. It is also an object to provide a speaker having a low impedance voice coil, the magnetictype' of pillow speakers having high impedance voice coils. I thus provide a complete speaker housed in a single case relatively flat in construction whichgives reproduction far superior to magnetic speakers with a metallic diaphragm. It is also an object of my invention to provide a voice coil fioatingly supported on the hollow core of the speaker cone and virtually within the concave area or side of the speaker cone.

These objects, together with other details and objects, will be more clearly set forth in the following specification and claims.

In the figures forming part of the application: Figure 1 is an exploded perspective View Of my speaker.

Pillow speakers heretofore 3 Claims. (01. 179-1155) Figure 2 is a sectional view thereof.

Figure 3 is a partial view of the speaker on the line 33 of Figure 2.

My speaker A is composed of a rear casing portion l preferably circular in shape which has formed on the outer edge thereof the annular lip portion In by placing the outer edge of the cone portion II which is crimped or turned inwardly of the rear casing portion l 9 as illustrated in Figure 2 to secure and support the perforated front casing portion l2 of the speaker A.

Secured to the inner surface of the rear casing portion I0 is the circular pot [3 to which is secured the circular or annular pot assembly washer plate M. The cylindrical permanent magnet I5 a; is secured to the inner lip I8 of the pot l3 so that the outer edge of the pot l3, the outer surface of the plate I4, and the outer surface of the magnet are virtually all in the same plane.

I further provide the cone I! which may be made of paper impregnated with ceramic and which is secured or clamped to the rear casing I l beneath the outer edge of the front casing portion l2 before the annular lip ii is turned over as illustrated in Figure 2. The cylindrical voice coil form I8 is secured centrally of the cone I! and projects slightly from the apex of the cone II, the cone I! having a hole or aperture formed therein adapted to receive the voice coil form 18. The major portion of the voice coil form l8 projects inwardly of the cone l1 and partially extends over the outward end of the magnet I5. The inside diameter of the voice coil form 18 is slightly larger than the outside diameter of the magnet l5 so that there is a slight clearance between the inner surface of the voice coil 88 and the outer surface of the magnet i5, thus allowing movement of the voice coil form over the magnet I5. I further provide the voice coil I 9 which is composed of fine wire wound upon the end of the voice coil form I 8.

Sufiicient clearance is provided between the voice coil 19 and the inner annular surface of the .pot assembly washer plate I4 so that the voice coil form 18, together with the coil l9 wound thereon, is free to move back and forth between the inner surfaceof the washer plate [4 and the outer surface of the magnet 55. This is necessary to allow the magnetic lines of force to follow around the outer edge of the pot is through the washer plate M where there is a concentration of the magnetic lines of force in the voice coil area.

The coil l9 has the leads 20 secured to the metal eyelets 2|, which eyelets 2| are secured in the wires protrude is covered by the cap member 29 which has formed at the bottom thereof the outlet opening 39 for the cord 28. The cap member 29 is secured over the recess portion 24 by means of the screw 3| which is threaded into the bottom portion of the recess 24.

The front casing portion l2 may be made of metal, plastic, or any suitable material, and has formed therein the perforations 32 to allow sound to travel therethrough. I further provide a dust cap 33 secured to the end of the voice coil form 18 which projects slightly from the apex of the cone l'l. This cap 33 may be made of felt or any suitable material.

Thus I have provided a speaker of the dynamic type but which does not have the present day pot construction assembly protruding from and outwardly of the apex of the cone of the speaker as found in present day dynamic speakers, As a result of my new construction I have produced a speaker which is extremely flat in nature, relatively speaking, but in which size is not sacrificed to produce a flat dynamic speaker.

I claim:

1. A relatively fiat dynamic speaker comprising a casing including an imperforatacircular, inwardl concave, rear casing wall having an outer edge portion comprising an annular lip, and a perforate, circular, inwardly concave, front casing wall, said annular lip being turned inwardly to engage the outer edge of said front casing wall and secure said walls together to'form said casing, a circular pot member secured to said rear casing wall and projecting forwardly thereof, an annular plate member within and secured to the forward end of said pot member, a cylindrical magnet axially aligned with said pot member and projecting forwardly within and spaced from said plate member, the outer edge of said rear casing wall and the forward ends of said pot member, said plate and said magnet terminating in substantially th same plane, a sound cone having its outer edge clamped between the outer edges of said casing walls by said lip and projecting forwardly within the front casing wall, an aperture in the apex of said cone, a cylindrical voice coil form within said aperture and secured to said cone, said form extending over the forward end portion of said magnet and spaced therefrom, a voice coil on the outer rearward end of said form, said coil being spaced from said plate member, whereby said voice coil form and voice coil are movable between said magnet and said annular plate member, and lead wire means leading from said voice coil to the exterior of said casing.

2. A relatively flat dynamic speaker comprising a casing including an imperforate, circular, inwardly concave, rear casing wall having an outer edge portion comprising an annular lip, and a perforate, circular, inwardly concave, front casing wall, said annular lip being turned inwardly to engage the outer edge of said front casing wall 4 and secure said walls together to form said casing, a pot member secured to said rear casin wall and projecting forwardly thereof, an apertured plate member within and secured to the forward end of said pot member, a, magnet axially aligned with said pot member and projecting forwardly within the aperture of said plate member and spaced from said plate member, the outer edge of said rear casing wall and the forward ends of said pot member, said plate and said magnet terminating in substantially the same plane, a sound cone having its outer edge clamped between the outer edges of said casing walls by said lip and projecting forwardly within the front casing wall, an aperture in the apex of said cone, a voice coil form within said aperture and secured to said cone, said form extending over the forward end portion of said magnet and spaced therefrom, a voice coil on the outer rearward end of said form, said coil being spaced from said plate member, whereby said voice coil form and voice coil are movable between said magnet and said plate member, and lead wire means leading from said voice coil to the exterior of said casing.

3. A relativel fiat dynamic speaker comprising a, casing including an imperforate, inwardly concave, rear casing wall having an outer edge a portion comprising a lip, and a perforate, circular,

inwardly concave, front casing wall, said lip being turned inwardly to engage the outer edge of said front casing wall and secure said walls together to form said casing, a pot member secured to said rear casing wall and projecting forwardly thereof, an apertured plate member within and secured to the forward end of said pot member, a magnet axially aligned with said pot member and projecting forwardly within the aperture of said plate member and spaced from said plate member, the outer edge of said rear casing wall and the forward ends of said pot member, said plate and said magnet terminating in substantially the same plane, a sound cone having its outer edge clamped between the outer edges of said casing walls by said lip and projecting forwardly within th front casing wall, an aperture in the apex of said cone, a voice coil form within said aperture and secured to said cone, said form extending over the forward end portion of said magnet and spaced therefrom, a voice coil on the outer rearward end of said form, said coil being spaced from said plate member, whereby said voice coil form and voice coil are movable between said magnet and said plate member, and lead wire means leading from said voice coil to the exterior of said casing.

JOSEPH D. ZIMMERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,995,080 Shotwell Mar. 19, 1935 2,091,011 Phelps et a1 Aug. 24, 1937 2,423,037 Marquis June 24, 1947 FOREIGN PATENTS Number Country Date 858,087 France Nov. 16, 1940 491,509- Great Britain Sept- 5, 1938 679,439 Germany Aug. 5, 1939 

